Post-traumatic stress disorder (PTSD) is a devastating illness that has substantial costs to Veterans, their families, and society. Although effective individual treatments for PTSD exist, high rates of treatment dropout and generally sub-optimal response rates remain common. Incorporating family members in treatment represents one potential avenue for improving outcomes, but existing family-inclusive treatments for PTSD are lengthy and burdensome to families and clinicians. To address this critical limitation, the applicant proposes a pilot effectiveness trial of a brief family intervention (BFI), to be delivered as an adjunct to Veterans? individual PTSD treatment. The two-session BFI protocol, which has been previously tested and found to be efficacious with family members of patients with obsessive-compulsive disorder, focuses on two primary family behaviors: increasing active support for treatment and reducing PTSD symptom accommodation, or family members? attempts to modify their own behavior or the environment in order to reduce Veterans? distress. Although often well-intentioned, accommodation directly conflicts with the goal of emotional exposure, a core target of current gold-standard PTSD treatments; effectively reducing accommodation therefore holds the potential to increase the ?dose? of treatment. In the proposed study, the BFI will be modified to increase its relevance to PTSD and will then be tested via a randomized controlled trial among family members of Veterans who are beginning a course of either PE or CPT. We propose that the BFI will exert its effects by reducing family member accommodation and increasing family members? active support for treatment (e.g., assisting with transportation to appointments or providing verbal encouragement); we further propose that these changes in family members will result in increased treatment engagement by patients and increased levels of ?exposure opportunities? (experiences of tolerating strong emotions in daily life). Our primary measures of the BFI?s effectiveness will be PTSD symptoms and treatment engagement among those Veterans whose family members receive it, compared to Veterans whose family members do not receive the BFI. PTSD symptoms will be assessed using the Clinician-Administered PTSD Scale (CAPS-5), and treatment engagement will be assessed using an existing measure of homework completion and a report of sessions attended, both to be completed by the treating clinician. We will use ecological momentary assessment, an advanced assessment strategy that allows for real-time data capture via smartphones, to explore the hypothesized mechanisms of the BFI?s effects in both family members and Veterans. We will also collect qualitative and quantitative pre-implementation data to examine the feasibility and acceptability of the BFI in a routine-care setting when delivered by trained usual care clinicians. These clinicians will be trained by the PI, who is the developer of the BFI, to deliver the intervention, and their feedback (along with that of the Veteran and family member participants) will allow for iterative revisions to the protocol in order to enhance its fit within this novel system and population. This study addresses an important public health concern by examining the effectiveness of a brief family intervention for the treatment of PTSD in a typical VA clinical setting. No such brief family-inclusive treatment for PTSD currently exists, either within or outside of the VA. Furthermore, the proposed research aims will complement a comprehensive training plan to prepare the applicant to become an independent investigator with expertise in mechanisms-based research design, along with advanced assessment and analytic approaches for future family-focused PTSD research. Results from the study will provide important information about whether or not this efficacious treatment can be effective and ready for further implementation efforts in routine-care settings.